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DP IB Biology: SL

Topic Questions

Home / IB / Biology: SL / DP / Topic Questions / 1. Cell Biology / 1.1 Cells: Theory / Structured Questions: Paper 2


1.1 Cells: Theory

Question 1a

Marks: 2
a)

In order to be considered living, organisms carry out the functions of life. 

Define the following:

  1. Homeostasis
  2. Excretion

[2 marks]

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    Key Concepts
    Functions of Life

    Question 1b

    Marks: 4
    b)

    The unicellular group, dinoflagellates, can be found in fresh water, preying upon other protozoa.

    Dinoflagellates contain eyespots and two flagella enabling them to find and move towards prey. Every day they undergo mitosis and in some cases this forms ‘red tides’. 

    State which functions of life have been described in this passage on dinoflagellates.

    [4 marks]

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      Key Concepts
      Functions of Life

      Question 2a

      Marks: 1
      a)

      Amoeba proteus is a unicellular organism that inhabits freshwater ponds and streams.

      At its largest size, Amoeba proteus can be visible to the naked eye. 

      State how the surface area to volume ratio changes as the Amoeba proteus grows.

      [1 mark]

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        Question 2b

        Marks: 1
        b)

        Gaseous exchange allows the Amoeba to undergo respiration. 

        State which aspect of the surface area to volume ratio has the greater effect on the rate of gaseous exchange.

        [1 mark]

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          Question 2c

          Marks: 1
          c)

          The contractile vacuole of the Amoeba helps maintain its osmotic equilibrium by excreting excess water from the cell. 

          State which aspect of the surface area to volume ratio would depend on this organelle.

          [1 mark]

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            Question 3a

            Marks: 2
            a)

            Glia and skeletal muscle cells are two examples of specialised cells. However, they were once stem cells. 

            Define the term stem cell. 

            [2 marks]

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              Key Concepts
              Stem Cells

              Question 3b

              Marks: 1
              b)

              The specialised cells mentioned in part (a) will differentiate when certain genes are expressed, as all cells contain the same genes.

              State the term used to describe an organism’s entire set of genes.

              [1 mark]

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                Key Concepts
                Gene Expression

                Question 3c

                Marks: 2
                c)

                It is hoped that our knowledge of stem cells can allow doctors to use them for therapeutic uses. 

                Describe how stem cells are being used to treat Stargardt’s macular dystrophy.

                [2 marks]

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                  Question 4a

                  Marks: 2
                  a)

                  The diagram below is of an Amoeba. The actual size, measured between points A and B, is 320 µm. 

                  When a student measured the same distance using an image from a microscope they determined the size to be 128 000 µm. 1-1-e-4a-paper-2

                  Calculate the magnification of this Amoeba. Show your working.

                  [2 marks]

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                    Question 4b

                    Marks: 2
                    b)

                    Whilst examining the Amoeba, the student also measured the length of the organelles present, including the nucleus. The length of the nucleus on the microscope image was 28 000 µm. 

                    If the student was examining the nucleus using the same magnification as part (a), in millimetres (mm), calculate the actual size of the nucleus. 

                    [2 marks]

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                      Question 4c

                      Marks: 1
                      c)

                      The freshwater habitats of Amoeba proteus may contain organisms that have more complex structures eg. freshwater snails. The snails have primitive gills enabling them to breathe under water and mucus-producing glands that allow them to hibernate when the water freezes.

                      Independently these structures have different properties but when combined they provide the snails with survival properties in the aquatic environment.

                      State the type of property that multicellular organisms, like the freshwater snail, have.

                      [1 mark]

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                        Key Concepts
                        Emergent Properties

                        Question 5a

                        Marks: 4

                        One mark is available for clarity of communication throughout this question.

                        a)

                        Draw a biological diagram of the Euglena sp. below.

                        1-1-e-5a-paper-2

                        [4 marks]

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                          Question 5b

                          Marks: 6
                          b)

                          Although almost all organisms conform to the cell theory, there are exceptions. 

                          List three examples and state why they are an exception to the theory.

                          [6 marks]

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                            Question 5c

                            Marks: 5
                            c)
                            Explain why cells differentiate, using examples within your answer.

                            [5 marks]

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                              Key Concepts
                              Cell Differentiation